If you have not applied for a U.S. passport, a Certificate of Citizenship is the only document you will need to file with your application. Otherwise, you have to present all the documents that together prove you are a U.S. citizen.

Unlike a U.S. passport, there is no expiration date on a Certificate of Citizenship.

Another curious thing is that the U.S. State Department issues the U.S. passport. This means that your citizenship is not necessarily “registered” with U.S. Citizenship & Immigration Services (“USCIS”). So, it’s possible that if an agency checks with USCIS, they could be told that there is no record that you are a U.S. citizen. We’ve had situations where people apply for government jobs, student aid, or loans and are told to bring back a Certificate of Citizenship. Their U.S. passport was not good enough evidence. Also, if the Department of Homeland Security (DHS) were ever to arrest you,the Certificate of Citizenship will be in your alien file. Hopefully, this would lead to you being released sooner than later once they learn you are a U.S. citizen. And make not mistake, DHS has definitely deported U.S. citizens “by accident.”

It looks to me that outside of Germany the German passport is accepted in most cases as proof of citizenship but inside of Germany there is this mess.

The Staatsangehörigkeitsausweis is said to be required for things like foreign marriage or adopting a foreign child even on governmental websites. I yet have to find specific cases where Staatsangehörigkeitsausweis was requested by anyone. If anyone knows something please let me know.